Light quantity control device

ABSTRACT

A light quantity control device includes: a bottom board having an opening; a first blade and second blade linearly moving in opposing directions and changing in an opening area of the opening; a supporting blade overlapping the first blade and closing the opening in cooperation with the first blade and second blade; and a driving lever connected to the first blade, the second blade, and supporting blade, and driving the first blade, second blade, and the supporting blade by rotation of the driving lever. The first blade and supporting blade are engaged with an identical pin provided in the driving lever. The first blade and supporting blade are misaligned in such a way to reduce an overlapping degree of the first blade and supporting blade. The first blade and supporting blade bring the opening to the fully closed state in cooperation with the second blade.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority toInternational Patent Application No. PCT/JP2007/065939 filed on Aug. 16,2007, which claims priority to Japanese Patent Application No.2006-245772 filed on Sep. 11, 2006, subject matter of these patentdocuments is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light quantity control device for acamera.

2. Description of the Related Art

Conventionally, there has been known a light quantity control device fora camera. In the conventional light quantity control device, at leasetwo blades are movably supported in opposing directions in a linearmanner relative to a bottom board having an opening, a rotationalmovement of a driving lever connected to these blades is changed to aliner movement, and the liner movement is outputted to the blades,thereby controlling the light quantity passing through the opening (seeJapanese Patent Application Publication No. 5-241224).

However, in the conventional light quantity control device, a firstblade and a second blade close the opening in cooperation with eachother, the first blade and the second blade are engaged with individualpins, respectively, which are provided in the driving lever. To providepins in such a way that movements of blades do not interfere, the arm ofthe driving lever has to be longer. Therefore, it is difficult todownsize the conventional light quantity control device.

SUMMARY OF THE INVENTION

It is therefore an object of present invention to provide a lightquantity control device downsized by a simple structure.

According to an aspect of the present invention, there is provided alight quantity control device including: a bottom board having anopening; a first blade and a second blade linearly moving in opposingdirections and changing in an opening area of the opening; a supportingblade overlapping the first blade and closing the opening in cooperationwith the first blade and the second blade; and a driving lever connectedto the first blade, the second blade, and the supporting blade, anddriving the first blade, the second blade, and the supporting blade byrotation of the driving lever. The first blade and the supporting bladeare engaged with an identical pin provided in the driving lever, thefirst blade and the supporting blade are misaligned in such a way toreduce an overlapping degree of the first blade and the supportingblade, and the first blade and the supporting blade bring the opening tothe fully closed state in cooperation with the second blade.

With such a configuration, the opening is brought to the fully openstate with the first blade overlapping the supporting blade, and thefirst blade and the supporting blade are misaligned in such a way toreduce an overlapping degree of the first blade and the supporting bladeand the first blade and the supporting blade bring the opening to thefully closed state in cooperation with the second blade. Therefore, thespace in which the blades are held can be reduced. Additionally, sincethe first blade and the supporting blade are engaged with the identicalpin provided in the driving lever, the light quantity control device canbe downsized by a simple structure without a provision of an elongatedarm of the driving lever and without an increase in engagement points.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be described indetail with reference to the following drawings, wherein:

FIG. 1 is an exploded perspective view of a light quantity controldevice when viewed from the top;

FIG. 2 is an exploded perspective view of the light quantity controldevice when viewed from the bottom;

FIGS. 3A to 3C show the action states of the blades;

FIGS. 4A to 4C are explanatory views of the position of a driving lever70 in a fully closed state;

FIGS. 5A to 5C are explanatory views of the slots formed on the blades;

FIGS. 6A to 6C are explanatory views of the difference in movingdistances of the blades due to a difference in shapes of the slots;

FIGS. 7A and 7B are explanatory views showing the degree of overlappingof a first blade 20 and a supporting blade 30;

FIG. 8 is an explanatory view of the misalignment degree of the firstblade 20 and the supporting blade 30 based on the slots shapedifferences between the first blade 20 and the supporting blade 30;

FIG. 9 is an explanatory view of a position of the driving leverdefining the small aperture state; and

FIG. 10 is an exemplary view of a second blade having a ND filter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will now be given, with reference to the accompanyingdrawings, an embodiment of the present invention.

A light quantity control device according to an embodiment of thepresent invention will be described below with reference to drawings.

FIG. 1 is an exploded perspective view of the light quantity controldevice when viewed from the top. FIG. 2 is an exploded perspective viewof the light quantity control device when viewed from the bottom.

A light quantity control device 1 includes: a blade-supporting plate 10;a first blade 20; a supporting blade 30; a plate 40; a second blade 50;a bottom board 60; a driving lever 70; and a motor portion 80.

The first blade 20, the supporting blade 30, and the second blade 50control a light quantity passing through an opening 61 formed in thebottom board 60 by using the movements thereof.

The blade-supporting plate 10 holds the blades and the like locatedbetween the blade-supporting platelO and the bottom board 60 in anoptical axis direction so as to restrict movements of the blades and thelike in the optical axis direction.

Additionally, the blade-supporting plate 10 has an opening 11 forcausing light to reach an image pickup device (not shown).

Further, the blade-supporting plate 10 has a receiving slot 13 and areceiving hole 12. The receiving slot 13 is located to face the opening11 and has an arc shape so as to receive a first pin 71 of the of thedriving lever 70. The receiving hole 12 for a second pin 72 of thedriving lever 70 has a semicircular shape.

An opening 21, for changing the opening area of the opening 61, isformed in the first blade 20 and shaped in such a manner to spread inthe entirety of the middle portion of the first blade 20. Additionally,the opening 21 also serves as a receiving hole for receiving the secondpin 72 formed on the driving lever 70.

The first blade 20 is formed with a slot 22, which is engaged with thefirst pin 71 formed in the driving lever 70, in a widthwise direction ofthe first blade 20. The slot 22 is a cam having an substantially L-shapebending in the partway thereof.

Further, the first blade 20 is formed with the guide slot 24 which isengaged with a guide pin 64 formed on the bottom board 60 and whichextends in a lengthwise direction of the first blade 20.

The supporting blade 30 has an opening 31 for changing the opening areaof the opening 61.

A slot 32 is engaged with the first pin 71 and linearly extends in thewidthwise direction of the supporting blade 30. Herein, the first blade20 and the supporting blade 30 are engaged with the first pin 71standing on the driving lever 70. Further, the supporting blade 30overlaps the first blade 20, and closes the opening 61 in conjunctionwith the first blade 20 and the second blade 50.

The supporting blade 30 has a receiving hole 33 for receiving themovement of the second pin 72 and the receiving hole 33 has an arcshape.

Further, the supporting blade 30 has a guide slot 34 engaged with theguide pin 64 and the guide slot 34 extends in the lengthwise directionof the supporting blade 30. In response to the moving distance of thesupporting blade 30, the guide slot 34 is shorter than the guide slot 24formed in the first blade 20.

The plate 40 is accommodated to be sandwiched between the supportingblade 30 and the second blade 50.

Furthermore, the plate 40 has an opening 41 for passing through thelight to reach the image pickup device.

In addition, the plate 40 has a receiving hole 42 for receiving thesecond pin 72 and the receiving hole 42 has an arc shape. The plate 40has a receiving hole 43 for receiving the first pin 71 and the receivinghole 43 has a semicircular shape.

The plate 40 has an engagement hole 44 fitted onto the guide pin 64,whereby the plate 40 is fixed and is not movable with respect to thebottom board 60.

The second blade 50 has a notch section at its edge and forms a cutout51. The second blade 50 has a slot 52 engaged with the second pin 72,and the slot 52 extends in a widthwise direction of the second blade 50.The slot 52 has an substantially L-shape that bents at a partway thereofand also serves as a cam.

The second blade 50 has a guide slot 54 engaged with the guide pin 64and the guide slot 54 extends in the moving direction of the secondblade 50.

The bottom board 60 has the opening 61, and a receiving hole 62 forreceiving the driving lever 70. Further, the guide pin 64, which isengaged with the guide slots 54, 34, and 24, and which is fitted intothe engagement hole 44, is formed at the proximity of the opening 61.Additionally, guide walls 65 are partially formed at ends of the bottomboard 60. The guide pin 64 and the guide walls 65 linearly guide thefirst blade 20, the supporting blade 30, and the second blade 50 in thelengthwise direction of the bottom board 60.

The driving lever 70 rotates about the center thereof within apredetermined angular range. The driving lever 70 has the first pin 71and the second pin 72 at both ends thereof, respectively, and the firstpin 71 and the second pin 72 protrude to the blades. Additionally, thedriving lever 70 is capable of being stopped in at least of one partwayposition between one end and the other end of its rotational range. Thatis to say, the rotation of the driving lever 70 drives the first blade20, the supporting blade 30 and the second blade 50, so that the lightquantity passing through the opening 61 of the bottom board 60 iscontrolled when the driving lever 70 is stopped at one end, the otherend or the partway position.

The motor portion 80 causes a rotational shaft to be connected to thecentral position of the driving lever 70, and drives the driving lever70.

The following will describe an actions of the blades.

FIGS. 3A to 3C show the action states of the blades, FIG. 3A shows thefully open state, FIG. 3B shows the fully closed state, and FIG. 3Cshows the small aperture state. Additionally, in FIGS. 3A to 3C, theblade-supporting plate 10, the plate 40, and the receiving hole 62 ofthe bottom board 60 are omitted. Further, shapes of the first blade 20and the supporting blade 30 are simplify illustrated.

The following will describe the fully open state in reference with FIG.3A.

The fully open state is maintained in such a manner that the opening 61is surrounded by the opening 21 formed in the first blade 20, theopening 31 formed in the supporting blade 30 and the cutout 51 formed inthe second blade 50.

The driving lever 70 is positioned to be substantially parallel with awidthwise direction of the light quantity control device 1.

The following will describe actions from the fully open state to thefully closed state.

As shown in FIG. 3A, the driving lever 70 rotates counterclockwise fromthe fully open state in which the driving lever 70 is positioned at theother end of the rotational range, so that the first blade 20 and thesupporting blade 30 are linearly moved in the right hand direction andthe second blade 50 is linearly moved in the left hand direction. Thatis to say, the first blade 20 and the supporting blade 30, and thesecond blade 50 are linearly moved in the opposing directions. The stateof the opening 61 is controlled to be in the fully closed state in whichthe driving lever 70 is positioned in the partway of the rotationalrange thereof. At this time, the fully closed state is maintained insuch a manner that the opening 61 is closed by the first blade 20, thesupporting blade 30, and the second blade 50.

The following will describe actions from the fully closed state to thesmall aperture state.

As shown in FIG. 3B, the driving lever 70 further rotatescounterclockwise from the fully closed state in which the driving lever70 is positioned at the partway of the rotational range, so that thefirst blade 20 and the supporting blade 30 are linearly moved in theleft hand direction and the second blade 50 is linearly moved in theright hand direction. As shown in FIG. 3C, the state of the opening 61is controlled to the small aperture state in which the driving lever 70is positioned in one end of the rotational range. The small aperturestate is maintained in such a manner that the opening 61 is defined byprofile of the opening 21 and that of the cutout 51.

As mentioned above, by the rotation of the driving lever 70, the stateof the opening 61 is controlled to the fully closed state from the fullyopen state, and to the small aperture state from the fully closed state.

The following will describe the position of the driving lever 70 indetail when the fully closed state is defined. FIGS. 4A to 4C areexplanatory views of the position of the driving lever 70 in the fullyclosed state.

FIG. 4A shows the driving lever 70 at the time when the opening 61 iscontrolled to the fully closed state, and a phantom line A passingthrough the rotational center P of the driving lever 70 and beingparallel in the moving direction of the blades. Moreover, each of α1 andα3 denote an angular range from the phantom line A to 45 degrees in theclockwise direction with the rotational center P set as a center. Eachof α2 and α4 denote an angular range from the phantom line A to 45degrees in the counterclockwise direction with the rotational center Pset as a center. Additionally, each of β1 and β2 denote the remainingangular range other than the above angular ranges.

In the fully closed state, the first pin 71 is positioned within theangular range α3, and the second pin 72 is positioned within the angularrange α1. That is to say, in the fully closed state, the driving lever70 is positioned within the angular ranges of 45 degrees in theclockwise direction from the phantom line A.

The following will describe an effect caused by positioning the drivinglever 70 in the position as mentioned above when the opening 61 isshifted to the fully closed state.

FIG. 4B shows the driving lever 70 slightly misaligned counterclockwisefrom the fully closed state shown in FIG. 4A. FIG. 4C shows the drivinglever 70 positioned within the rotational range β1, and β2, and slightlymisaligned counterclockwise. In addition, the misaligned angles of thedriving lever 70 shown in FIGS. 4B and 4C are substantially identical.

As shown in FIG. 4B, when the driving lever 70 is slightly misaligned,the center of the second pin 72 is misaligned by D1 in the movingdirection of the blades.

On the other hand, as shown in FIG. 4C, when the driving lever 70 isslightly misaligned, the center of the second pin 72 is misaligned by D2in the moving direction of the blades.

When D1 is compared with D2, the rotational angles caused bymisalignment of the driving lever 70 are substantially identical,however, the misalignment degrees of the blade in the moving directionsare greatly different. D1 is smaller than D2. Additionally, D1 and D2directly indicate the degrees of the misalignment in the movingdirection of the blades. That is, even if the rotational range of themisalignment of the driving lever 70 are substantially identical, eachblade is greatly misaligned in the moving direction based on theposition of the driving lever 70.

As stated heretofore, the driving lever 70 is positioned within 45degrees with respect to the phantom line A in the clockwise direction,when the first blade 20, the supporting blade 30 and the second blade 50control the state of the opening 61 to the fully closed state.Therefore, even if when the driving lever 70 is slightly misaligned fromthe fully closed state, a displacement of each blade is not greatlyaffected. Consequently, even if the positional accuracy is roughly set,the fully closed state can be maintained with certainty.

Additionally, even if the second pin 72 is positioned within α2 and thefirst pin 71 is positioned within α4 at the time when the state of theopening 61 is controlled to be in the fully closed state, that is tosay, even if the driving lever 70 is positioned within 45 degrees withrespect to the phantom line A in the counterclockwise direction, theabove effect can be attained. Consequently, by setting the driving lever70 to be positioned within 90 degrees centering on the phantom line A,the above effect is attained.

Further, by setting the driving lever 70 to be positioned within theabove range at a time when the state of the opening 61 is in the fullyopen state or the small aperture state as well as the fully closedstate, the above effect is attained.

As well as setting the driving lever 70 to be positioned within 90degrees, it may be positioned within 80 or 70 degrees centering on thephantom line A. Additionally, the driving lever 70 may be set to besubstantially parallel with the phantom line A.

The following will describe the slots formed on the blades.

FIGS. 5A to 5C are explanatory views of the slots formed on the blades.

FIG. 5A shows the first blade 20.

In the first blade 20, the slot 22 is formed apart from the opening 21and is formed in a region more than a half of the first blade 20 in awidthwise direction. The slot 22 is a cam having a shape of asubstantially L-shape that bends at the partway, namely, a bendingportion 22 a. In the slot 22, the bending portion 22 a is closer to theopening 21.

FIG. 5B shows the second blade 50.

In the second blade 50, the slot 52 is formed apart from the cutout 51and is formed in a region more than a half of the second blade 50 in awidthwise direction. The slot 52 is a cam having a shape of asubstantially L-shape that bends at the partway, namely, a bendingportion 52 a. In the slot 52, the bending portion 52 a is closer to anopposing side of the cutout 51.

FIG. 5C shows the supporting blade 30.

In the supporting blade 30, the slot 32 is formed in the proximity ofthe receiving hole 33. The slot 32 is formed in a region that occupiesmore than a half of the supporting blade 30 in a widthwise direction,and is also formed linearly to slightly tilt in the widthwise direction.

Such slots are formed in the widthwise direction of blades. Therefore,the driving lever 70 can be positioned within 90 degrees with thephantom line A set as a center.

The following will describe relationships between the shape of the slotand the moving distance of the blade.

FIGS. 6A to 6C are explanatory views of the difference in movingdistances of the blades due to a difference in shapes of the slots.

FIG. 6A shows a change in the position of the slot 52 in response to therotation of the second pin 72. Additionally, for clearly showing thepositions of the second pin 72 and the slot 52 in each state, in FIGS.6A and 6B, the positions of the second pin 72 and the slot 52 in thefully open position, the fully closed position, and the small apertureposition are indicated by (a), (b), and (c) respectively. Further, thesecond pin 72 rotates about the rotational center P within apredetermined range.

In the fully open state (a), the second pin 72 is positioned at one endof the slot 52. At this time, the slot 52 is positioned in the slightlyright side of the rotational center P.

The second pin 72 rotates counterclockwise from the fully open state(a), so that the second pin 72 is positioned at the fully closedposition (b) in which the second pin 72 comes closer to the bendingportion 52 a of the slot 52. At this time, the slot 52 is positionedsubstantially in the left side of the rotational center P (e.g., opening61 side). L1 indicates the moving distance of the slot 52 from the fullyopen position (a) to the fully closed position (b).

Next, the second pin 72 further rotates counterclockwise from the fullyclosed position (b) to the small aperture position (c), and ispositioned at the other end of the slot 52. The slot 52 is positionedagain in the right side (that is, in such a direction as to move awayfrom the opening 61) when the second pin 72 is positioned at the smallaperture position (c) form the fully closed position (b).

As mentioned above, when the driving lever 70 lies within the above 90degrees, the bending portion 52 a of the slot 52 is closer to therotational center P of the driving lever 70. Specifically, the slot 52is shaped to protrude relative to a rotational trace of the second pin72.

The following will describe the slot 52 shaped in a liner shapeperpendicular to a moving direction the blade.

FIG. 6B shows a change in the position of the slot in response to therotation of the second pin 72, if the slot is formed to be vertical withthe moving direction of the blades. Additionally, a slot 52 g denotesthe slot to be linearly shaped. Further, FIG. 6B shows the slots 52g(a), 52 g(b), and 52 g(c) corresponding to the above mentioned slots52(a) 52(b), and 52(c), respectively.

L2 indicates the moving distance of the slot 52 g from the position (a)to the position (b).

When the moving distance L1 shown in FIG. 6A is compared with the movingdistance L2 shown in FIG. 6B, the moving distance L1 is longer than themoving distance L2.

FIG. 6C shows the shape of the slot 52. As shown in FIG. 6C, when Δmdenotes a distance from the bending portion 52 a to the end of the slot52 in the moving direction, the second blade 50 greatly moves in theleft hand direction by Δm.

As mentioned above, since the slot 52 is formed such that the bendingportion 52 a is located closer to the rotational center P, when thedriving lever 70 lies in the above range of 90 degrees, the movingdistance of the second blade 50 moved by the rotation of the drivinglever 70 can be increased.

Additionally, likewise, the slot 22 formed in the first blade 20 has thesimilar function of the slot 52. This greatly increases the relativemoving distances of the first blade 20 and the second blade 50. Bygreatly increasing the relative moving distances of the first blade 20and the second blade 50, even if the opening 61 has a lager size thanthat of each blade or that of the bottom board 60, the state of theopening 61 can be controlled from the fully open state to the fullyclosed state. Further, the blades or the bottom board 60 can be madesmaller with the size of the opening 61 assured. This downsizes thewhole light quantity control device.

Additionally, the plate 40 is sandwiched between the supporting blade 30and the second blade 50. The moving distance of the supporting blade 30is smaller than that of the first blade 20, but the supporting blade 30moves in the same direction of the first blade 20. The plate 40 has anability of buffering the movements of the second blade 50 and thesupporting blade 30 that moves in the opposing direction of the secondblade 50. This smoothes the movements of the blades, and preventsabrasion thereof.

The following will describe the relationship between the first blade 20and the supporting blade 30.

FIGS. 7A and 7B are explanatory views showing the degree of overlappingof the first blade 20 and the supporting blade 30.

FIG. 7A is an enlarged view of the periphery of the opening 61 in thefully open state. FIG. 7B is an enlarged view of the periphery of theopening 61 in the fully closed state.

As shown in FIG. 7A, the first blade 20 and the supporting blade 30 areheld by the bottom board 60 with the opening 61 opened. Additionally,the first blade 20 and the supporting blade 30 are held such that apredetermined region of the first blade 20 and that of the second blade30, covering the opening 61 when the fully closed state is defined, areheld within a space S. The space S indicates a distance from the leftedge of the opening 61 to the left end of the bottom board 60.

L indicates a distance in which the first blade 20 and the supportingblade 30 are overlapped with each other.

When shifted to the fully closed state, as shown in FIG. 7B, the firstblade 20 and the supporting blade 30 covers the opening 61 such a way toreduce the degree of overlapping of the first blade 20 and thesupporting blade 30. When ΔL denotes a misalignment degree ofoverlapping of the first blade 20 and the supporting blade 30, adistance of an area, in which the opening 61 is covered with the firstblade 20 and the supporting blade 30, can be expressed by L+ΔL.

As mentioned heretofore, the first blade 20 and the supporting blade 30are overlapped with each other so as to bring the opening 61 to thefully open state. Next, the degree of overlapping of the first blade 20and the supporting blade 30 is reduced, as if the first blade 20 and thesupporting blade 30 extended, then the first blade 20, the supportingblade 30, and the second blade 50 bring the opening 61 to the fullyclosed state. Therefore, the space in which the first blade 20 and thesupporting blade 30 are held can be reduced. This also downsizes thelight quantity control device.

The following will describe the misalignment degree of the first blade20 and the supporting blade 30 based on the shape differences of thefirst blade 20 and the supporting blade 30.

FIG. 8 is an explanatory view of the misalignment degree of the firstblade 20 and the supporting blade 30 based on the shape differencesbetween the first blade 20 and the supporting blade 30. Additionally, toclearly show positions of the first pin 71 and the slot 32 in eachstate, 32(a) and 32(b) respectively denote the slot 32 in the fully openposition and the fully closed position. Likewise, 71(a) and 71(b)respectively denote the first pin 71 in the fully open position and thefully closed position. Also, how the slot 32 and the first pin 71 arechanged is shown on the basis of the slot 22.

As shown in FIG. 8, the slot 32 is positioned on the right side of theslot 22 in the fully open position (a) of the first pin 71.Additionally, the first pin 71 is positioned at the lower ends of theslots 22 and 32.

The first pin 71 rotates counterclockwise from the fully open position(a), and is positioned in the fully closed position (b) near the bendingportion 22 a of the slot 22. The position of the slot 32 with the firstpin 71 positioned in the fully closed position (b) is misaligned andshifted to the left side from the position of the slot 32 with the firstpin 71 positioned in the fully open position (a). The misalignmentdegree at this time is represented by ΔL. This misalignment shown inFIGS. 7A and 7B caused by moving the first blade 20 and the supportingblade 30, because the slot 22 and the slot 32 are differ in the shapefrom each other. With such a configuration, the overlapping degree ofthe first blade 20 and the supporting blade 30 can be changed betweenthe time when the opening 61 is brought to the fully closed state andthe time when the opening 61 is brought to the fully open state.

The following will describe the position of the driving lever 70defining the small aperture state.

FIG. 9 is an explanatory view of a position of the driving leverdefining the small aperture state.

FIG. 9 shows the receiving hole 62 formed in the bottom board 60 and thedriving lever 70 when the small aperture state is defined.

The receiving hole 62 is shaped into a substantially circular shape, andis formed with stopper portions 63 such that an inner profile of thereceiving hole 62 are partially curved to project to a center thereof.The stopper portions 63 are located at respective two positions in asymmetric manner with respect to the center of the receiving hole 62.

When the small aperture state is defined, the driving lever 70 isrestricted to rotate counterclockwise by abutting the first pin 71 andthe second pin 72 with the stopper portions 63.

Therefore, when the driving lever 70 is positioned at an end of therotational range defined by the stopper portions 63, each blade bringsthe opening 61 to the small aperture state, whereby the opened degreecan be constant in the small aperture state. Consequently, the smallaperture state is defined with high accuracy.

Further, the stopper portions 63 are integrally formed with the bottomboard 60. With such a configuration, the rotational range of the drivinglever 70 can be restricted by a simple structure.

Additionally, the first blade 20, the supporting blade 30, and thesecond blade 50 bring the opening 61 to the fully open state when thedriving lever 70 is positioned at the other end of the rotational rangethereof, and bring the opening 61 to the fully closed state when thedriving lever 70 is positioned at a partway of the rotational rangethereof. This configuration maintains the fully open state, the fullyclosed state, and the small aperture state in the opening 61.

Further, the first blade 20, the supporting blade 30 and the secondblade 50 are configured such that the moving directions thereof whilethe driving lever 70 rotates from one end of the rotational range to thepartway position thereof are respectively opposite to those while thedriving lever 70 rotates from the above partway position to the otherend thereof. Therefore, while the driving lever 70 rotates from one endof the rotational range to the partway position thereof, each of theabove blades is shifted from the small aperture position to the fullyclosed position. While the driving lever 70 rotate from the partwayposition of the rotational range to the other end thereof, each of theabove blade is shifted from the fully closed position to the fully openposition.

Additionally, the slots 22 and 52 are shaped into a cam shape in thewidthwise direction of each blade. With such a configuration, each bladeis easily moved to the small aperture position, the fully closedposition, and the fully open position in response to the rotationalposition of the driving lever 70.

The following will describe a modification of the light quantity controldevice.

A second blade 50A, according to a modification of the light quantitycontrol device, has a ND filter at the cutout 51. FIG. 10 is anexemplary view of the second blade 50A having the ND filter. The NDfilter 51A is provided to cover the opening 61 when the driving lever 70is positioned at one end of the rotational range, that is to say, wheneach blade is positioned at the small aperture position.

In this manner, at least one of the blades may be provided with the NDfilter.

While the preferred embodiment of the present invention has beenillustrated in detail, the present invention is not limited to theabove-mentioned embodiment, and other embodiments, variations andmodifications may be made without departing from the scope of thepresent invention.

In the above embodiment, as shown in FIGS. 3A to 3C, the rotation of thedriving lever in one direction allow the fully open state to be shiftedto the fully closed state, and the fully closed state to be shifted tothe small aperture state. However, the present invention is limited tothe configuration, for example, the fully closed state may be shifted tothe fully open state, and the fully open state may be shifted to thesmall aperture state.

Additionally, although the number of stop positions of the driving leveris three in the embodiment, and the stop positions may be two includingone end and the other end. In this case, the driving lever 70 rotateswithin 90 degrees with a phantom line set as center, the phantom linepassing through the rotational center of the driving lever 70 and beingparallel with moving direction of blades.

Movements of the first blade 20, the supporting blade 30, and the secondblade 50 may allow the quantity of the light passing through the opening41, which is smaller than the opening 61 formed on the bottom board 60,formed on the plate 40.

Only the first blade 20 and the second blade 50 may control the quantityof the light passing through the opening 61 without the provision of thesupporting blade 30. Additionally, in this case, the plate 40 isarranged between the first blade 20 and the second blade 50, therebybuffering the sliding of both blades.

Finally, several aspects of the present invention are summarized asfollows.

According to an aspect of the present invention, there is provided alight quantity control device includes: a bottom board having anopening; a first blade and a second blade linearly moving in opposingdirections and changing in an opening area of the opening; a supportingblade overlapping the first blade and closing the opening in cooperationwith the first blade and the second blade; and a driving lever connectedto the first blade, the second blade, and the supporting blade, anddriving the first blade, the second blade, and the supporting blade byrotation of the driving lever. The first blade and the supporting bladeare engaged with an identical pin provided in the driving lever, thefirst blade and the supporting blade are misaligned in such a way toreduce an overlapping degree of the first blade and the supportingblade, and the first blade and the supporting blade bring the opening tothe fully closed state in cooperation with the second blade.

With such a configuration, the opening is brought to the fully openstate with the first blade overlapping the supporting blade, and thefirst blade and the supporting blade are misaligned in such a way toreduce an overlapping degree of the first blade and the supporting bladeand the first blade and the supporting blade bring the opening to thefully closed state in cooperation with the second blade. Therefore, thespace in which the blades are held can be reduced. Additionally, sincethe first blade and the supporting blade are engaged with the identicalpin provided in the driving lever, the light quantity control device canbe downsized by a simple structure without a provision of an elongatedarm of the driving lever and without an increase in engagement points.Additionally, the first blade and the supporting blade may have slotseach shaped into different shapes such that moving distances of theblades are different.

With such a configuration, the overlapping degree of the first blade andthe supporting blade can be changed between the time when the opening isbrought to the fully closed state and the time when the opening isbrought to the fully open state. Therefore, the supporting blade isprevented from improperly moving and the light quantity control devicecan be downsized by a simple structure.

Further, a slot of the first blade and a slot of the supporting blademay be formed in widthwise directions of the first blade and thesupporting blade, respectively, the slot of the supporting blade islinearly shaped, and the slot of the first blade is a cam having asubstantially L shape.

With such a configuration, moving distances of the first blade and thesupporting blade are different with ease.

1. A light quantity control device comprising: a bottom board having anopening; a first blade and a second blade linearly moving in opposingdirections and changing an opening area of the opening; a supportingblade overlapping the first blade and closing the opening in cooperationwith the first blade and the second blade; and a driving lever connectedto the first blade, the second blade, and the supporting blade, anddriving the first blade, the second blade, and the supporting blade byrotation of the driving lever, wherein the first blade and thesupporting blade are engaged with an identical pin provided in thedriving lever, the first blade and the supporting blade are misalignedin such a way to reduce an overlapping degree of the first blade and thesupporting blade, and the first blade and the supporting blade bring theopening to the fully closed state in cooperation with the second blade,wherein the driving lever has a shape extending in a predetermineddirection and the predetermined direction is capable of being parallelwith the moving directions of the blades.
 2. The light quantity controldevice according to claim 1, wherein the first blade and the supportingblade have slots each shaped into different shapes such that movingdistances of the blades are different.
 3. The light quantity controldevice according to claim 2, wherein a slot of the first blade and aslot the supporting blade are formed in widthwise directions of thefirst blade and the supporting blade, respectively; the slot of thesupporting blade is linearly shaped; and the slot of the first blade isa cam having a substantially L shape.
 4. The light quantity controldevice according to claim 1, wherein a slot of the first blade and aslot of the supporting blade are formed in widthwise directions of thefirst blade and the supporting blade, respectively; the slot of thesupporting blade is linearly shaped; and the slot of the first blade isa cam having a substantially L shape.